The heart is the center of a person's circulatory system. It includes an electromechanical system performing two major pumping functions. The left side of the heart draws oxygenated blood from the lungs and pumps it to the organs of the body to supply their metabolic needs for oxygen. The right side of the heart draws deoxygenated blood from the body organs and pumps it to the lungs where the blood gets oxygenated. These pumping functions result from contractions of the myocardium (cardiac muscles). In a normal heart, the sinoatrial (SA) node, the heart's natural pacemaker, generates electrical impulses, called action potentials, that propagate through an electrical conduction system to various regions of the heart and excite the myocardial tissues of these regions. Coordinated delays in the propagations of the action potentials in a normal electrical conduction system cause the various portions of the heart to contract in synchrony and result in efficient pumping function.
A blocked or otherwise damaged electrical conduction system causes irregular contractions of the myocardium, a condition generally known as arrhythmia. Arrhythmia reduces the heart's pumping efficiency and hence diminishes the blood flow to the body. A deteriorated myocardiurn has decreased contractility, also resulting in diminished blood flow. A heart failure patient usually suffers from both a damaged electrical conduction system and a deteriorated myocardium. For example, a large percentage of heart failure patients also experience atrial fibrillation (AF), which may affect effectiveness of therapies treating heart failure. To improve efficacy of heart failure therapies, there is a need for monitoring incidence of AF in heart failure patients.